This invention relates to a seat reclining device, and more particularly, the present invention pertains to a structure of the seat reclining device which is capable of receiving an excessive load.
A seat reclining device which is capable of receiving an excessive load is disclosed in U.S. Pat. No. 5,816,656. This known seat reclining device has a lower arm fixed to a seat cushion, an upper arm disposed at a seat back side and capable of rotating with the lower arm, and a locking mechanism which restricts rotation of the upper arm relative to the lower arm. To receive an excessive load, the strength of the device is improved by combining a pair of reclining mechanisms which are constructed with a symmetrical shape to one another. This strengthened seat reclining device is utilized for supporting one side of the seat back where the seat belt is anchored. The seat reclining device supports an excessive load transmitted from the seat belt upon an emergency condition such as a frontal collision of the vehicle.
However, the strength of the above reclining device is achieved by providing the lower arms, the upper arms and the locking mechanisms in pairs respectively. Accordingly, the number of parts is increased as is the manufacturing cost.
Therefore, a need exists for a reclining seat having improved strength without increasing the number of parts to the same extent as in the known reclining device.
According to one aspect of this invention, a seat reclining device includes a first arm supported by one a seat cushion or a seat back, a second arm supported by the other of the seat cushion and the seat back, and rotatably supported with respect to the first arm, a first circular concave portion formed in the first arm, a second circular concave portion formed in the first arm inside the first concave portion, and a pawl provided with a first outer gear portion and a second outer gear portion each having a plurality of gear teeth. A first inner gear portion having a plurality of gear teeth is formed on the inner peripheral portion of the first circular concave portion, with the first inner gear portion being engageable with the first outer gear portion. A second inner gear portion having a plurality of gear teeth is formed on the inner peripheral portion of the second circular concave portion, with the second inner gear portion being engageable with the second outer gear portion.
The seat reclining device is able to lock the position of the seat back relative to the seat cushion by engaging the first and second engaging portions of the pawls with the first and second engaged portions of the first arm.
According to another aspect, a seat reclining device includes a first arm supported by a seat cushion or a seat back, and a second arm rotatably supported with respect to the first arm and supported by the other of the seat cushion and the seat back. The first arm possesses a first annular recessed portion having an inner diameter, with the first annular recessed portion having a circumferentially extending inner periphery at which is provided a first inner toothed portion and with the first inner toothed portion extends along at least a portion of a circumferential extent of the inner periphery of the first annular recessed portion. The first arm also possesses a second annular recessed portion having an inner diameter different from the inner diameter of the first annular recessed portion. The second annular recessed portion has a circumferentially extending inner periphery at which is provided a second inner toothed portion, with the second inner toothed portion extending along at least a portion of a circumferential extent of the inner periphery of the second annular recessed portion. A plurality of pawls are positioned between the first and second arms, with each of the pawls possessing a first outer toothed portion and a second outer toothed portion, and with the first outer toothed portion and the second outer toothed portion of each pawl being offset from one another. The first outer toothed portion on each pawl is engageable with the first inner toothed portion to rotatably fix the first and second arms relative to one another, and the second outer toothed portion on each pawl is engageable with the second inner toothed portion.
According to another aspect, a seat reclining device includes a first arm supported by a seat cushion or a seat back, and a second arm supported by the other of the seat cushion and the seat back, with the first and second arms being supported for relative rotation about a rotational axis. The first arm is provided with an annularly arranged first inner toothed portion centered on the rotational axis and an annularly arranged second inner toothed portion centered on the rotational axis, with the second inner toothed portion being spaced from the rotational axis by a radial distance different from the radial distance between the first inner toothed portion and the rotational axis. A pawl is slidably positioned between the first and second arms for slidably moving towards and away from the rotational center. The pawl possesses a first outer toothed portion and a second outer toothed portion, with the first outer toothed portion of the pawl and the second outer toothed portion of the pawl being offset from one another. The first outer toothed portion on the pawl is adapted to be engaged with the first inner toothed portion and the second outer toothed portion on the pawl is adapted to be engaged with the second inner toothed portion.